The present invention relates to a circuit module having a circuit board on which heat-generating circuit elements and a heatsink for radiating heat generated by the elements are mounted. The invention also relates to a portable apparatus such as a portable computer, which has a housing containing the circuit module. Particularly, the invention relates to a structure which secures the heatsink to the circuit board.
In recent years, book-type and notebook-type portable computers have remarkably advanced in operating efficiency. In particular, the data-processing speed of CPUs for use in portable computers has been increasing. A CPU of this type is packaged in the form of a single module. The CPU module is mounted on the circuit board provided in the housing of a portable computer.
The faster the CPU processes data, the more power it consumes, and the more heat it generates. When a CPU which generates much heat while operating is provided in a housing, it is necessary to radiate the heat with high efficiency in the housing.
Hitherto, a heatsink is attached to the circuit board on which a CPU is mounted and set in contact with the CPU in order to promote the heat radiation from the CPU. The heatsink has a heat-radiating panel to which heat is transmitted from the CPU. The panel has a number of fins for radiating heat. The panel is supported on the circuit board and exposed within the housing. Natural radiation of the heat transmitted from the CPU to the panel is achieved through the heat-radiating panel in the housing.
The conventional heatsink has a plurality of supports. The circuit board has a plurality of seats, which have a screw hole each. The supports are laid on the seats and fastened thereto by screws. The heatsink is thereby secured to the circuit board.
Portable computers recently developed have housings reduced in size to meet the demand made in the market. There is the trend that the space available in the housing decreases. The circuit board can no longer have its component-mounting area increased. To make matters worse, the component-mounting area is reduced by the total area of the seats which support the heatsink. Consequently, the designer may find it difficult to arrange the circuit component required, including not only the CPU but also various connectors and other components (e.g., a DRAM), in the limited component-mounting area. In the worst case, the component-mounting area may be too small to hold all circuit components.